Dye Removal Research Articles

Novel hydrogel based on natural hybrid backbones: optimized synthesis and effective adsorbent for the removal of malachite green dye from an aqueous solution

Novel hydrogel based on natural hybrid backbones: optimized synthesis and effective adsorbent for the removal of malachite green dye from an aqueous solution

Characterization and applicability of the Naima–Tiaret–Algeria illite-montmorillonite clay for methylene blue dye removal: adsorption kinetic, isotherm and thermodynamic studies

Abstract An illite-montmorillonite clay from Naima, IMN (Algeria) was treated via physical and chemical treatment (TIMN) and investigated for the removal of methylene blue. IMN and TIMN clays were characterized by XRD, XRF, SEM-EDS, DSC-GA, FTIR and DC electrical conductivity methods. To analyze the sorption behavior of MB on the clays, a mechanistic model for interpreting the sorption data was developed. IMN clay revealed high sorption capacity (1.925 × 10−2 kg kg−1) for MB in 60 min. The pseudo-second-order model had a very good agreement to describe the MB adsorption process. The adsorption capacities, qe,exp, of 4.327 × 10−2 and 4.914 × 10−2 kg kg−1 for IMN and TIMN, respectively, were obtained. The free energy from the D–R model from adsorbing MB using IMN and TIMN ranged from 1.581 to 0.745 × 10−3J mol−1, respectively, suggesting that the process is physisorption. Besides, the sorption process was more sensible to temperatures that increase was beyond 40 °C causing a decrease in adsorption capacity, indicating that the adsorption reaction of MB onto IMN was exothermic. The adsorption mechanism of I/M clay to remove MB was likely based on hydrogen bonding, electrostatic attraction, cation exchange and n–π interaction. These results proved that TIMN was a promising adsorbent for removing MB from its simulated wastewater.

Bioremediation of reactive black 5 textile dye wastewater using bacterial exopolysaccharides

Purpose The purpose of this paper is to investigate the efficacy of bacterial exopolysaccharides (Eps) in reactive black 5 (RB5) textile dye wastewater bioremediation. Design/methodology/approach The Eps were produced by bacteria isolated from cotton gin trash soils collected from different cotton-growing regions in Kenya for comparison purposes. A broth medium reconstituted using molasses was assessed for its capacity to produce the Eps. RB5 textile dye wastewater was optimized for dye removal under different temperatures, times and molasses concentrations. Dye removal was studied by Lovibond-Day Light Comparator, UV–Vis spectrophotometer and FTIR. Findings It was found that cotton gin trash soils contained Eps-producing bacteria. Three of the Eps studied were found to have the capacity to remove at least 80% of the dye from the wastewater. Research limitations/implications This research did not assess the efficacy of the RB5 dye removal from the wastewater by mixtures of the Eps. Practical implications Bioremediation of textile dye wastewater with Eps produced by bacteria cultured from cotton gin trash soil is significant because it will offer an effective and cleaner alternative to the chemical coagulants. Social implications Alternative treatment of textile wastewater with the Eps would result in safer water being released into the water bodies as opposed to the chemically treated wastewater that contains remnant chemicals. Originality/value Research on the use of Eps produced by bacteria isolated from cotton gin trash soils for removal of RB5 dye from textile wastewater has not been done before.

Structural simulation and performance evaluation of a novel synthesized ZIF in the adsorption of MO from aqueous solutions.

Zeolitic imidazolate frameworks (ZIFs) are desirable materials widely applied as adsorbent for wastewater treatment. This study synthesizes and applies a novel structured ZIF with organic ligand of 2-methyl imidazole and metal salt of copper (II) sulfate as adsorbent. Its morphology and structure were investigated using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, field emission scanning electron microscope, energy dispersive X-ray spectrometry, and mapping analysis. After structural analysis, the adsorbent structure was simulated and determined using Avogadro and Gaussian software. The removal efficiency of prepared ZIF in the removal of methyl orange from aqueous solution was evaluated. The effect of pH, the concentration of the dye in solution, dosage of the adsorbent, and the contact time between adsorbent and solution on the methyl orange removal were examined using central composite design of response surface methodology in five levels. The maximum dye removal of 99% was obtained for 2g adsorbent/L, pH of 3.3, and initial dye concentration of 121mg/L after 127min contact time. In addition, to reduce the economic costs and energy consumption, the synthesis time was also reduced and used to show the applicability of the adsorbent prepared and understand its advantages and disadvantages in removing methyl orange dye from aqueous solutions. This molecular adsorbent is stable, and it can be stored for months. On the other hand, this ZIF can be easily recovered and reused many times. In this research, after five times of recovery, there was no significant change in the effectiveness of the adsorbent.

A Cellulose‐Based Adsorbent using Box‐Behnken Design for the Adsorption of Reactive Blue 19 Dye from Simulated Wastewater

AbstractThis study attempts a successful synthesis of a cellulose‐based adsorbent using orthophosphoric acid as a chemical activating agent followed by pyrolysis. A detailed characterization of synthesized adsorbent in terms of its morphology, material crystallinity, and surface area was studied. Batch studies were performed to remove reactive blue 19 dye from its simulated wastewater. The impact of various adsorption parameters such as adsorbent dosage (A: 0.1 to 0.5 g), initial dye concentration (B: 100 to 500 mg/L), contact time (C: 10 to 180 min), pH (D: 2 to 10), temperature (E: 35 to 60 °C) were examined and optimized using on Box‐Behnken method with Response Surface Methodology. The experimentally obtained adsorption data were fitted to different isotherms and kinetic models. The findings prove that more than 96 % of 400 mg/L of RB19 dye removal is possible with 4 g/L dosage in 18.5 min at 50 °C with its original pH of 6.8. Also, three cycles of regenerability and reusability of CBA gives 51.88 % of RB19 dye removal. Moreover, the possibility of using spent adsorbent in the boiler as a fuel was explored. Consequently, this research will contribute to SDG6 by maintaining circularity and sustainability in the entire process.

Application of artificial neural networks and Langmuir and Freundlich isotherm models to the removal of textile dye using biosorbents: A comparative study among methodologies

AbstractAdsorption isotherms are valuable tools for describing the interaction between adsorbate and adsorbent since they demonstrate the equilibrium relationship. The Langmuir and Freundlich models are the most commonly used isotherm models to describe these relationships; still, they cannot consistently deliver efficient results due to the assumptions of the model not predicting more complex situations as occurs in biosorption. Artificial neural networks (ANN) are a set of algorithms modelled loosely after the human brain and are designed to recognize patterns. The ANN tool can overcome problems isotherm models have in describing the interactions mentioned and help define the best conditions for a given adsorption process. This paper reports the application of ANNs for predicting the removal efficiency of textile dye Neolan Black WA (Acid Black 52) using orange peel and sugarcane bagasse as biosorbents. The Freundlich, Langmuir, pseudo‐first‐order, and pseudo‐second‐order models were applied and compared to the ANN model. The parameters evaluated were initial dye concentration (10–600 mg/L), final dye concentration (0–83.44 mg/L), biosorbent mass (1.5 g), pH (2), and contact time of dye (0.167–24 h). Two classes of ANNs, Elman and feed‐forward networks, were tested with a mean square error of 0.0212 and 0.7274 for the isotherm and kinetics, respectively. Compared to the conventional isotherm and kinetic models, the Elman network predicted the amount adsorbed by the biosorbents with higher precision, acquiring a determination coefficient of 0.9998 and a mean square error of 8.75 × 10−5.

Starch-Grafted Polyacrylic Acid Copolymer with Acrylamide: An Advanced Adsorbent for Victoria Green B Dye Removal and Environmental Remediation

AbstractA new adsorbent, starch grafted polyacrylic acid copolymer with polyacrylamide (SG@AA-co-AM), was synthesized using free radical polymerization techniques. Proton nuclear magnetic resonance (1H NMR), Fourier-transform infrared spectrophotometry (FTIR), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), particle size distribution (PSD), and fluorescent electron microscopy (FEM) were employed to elucidate the structure, crystalline nature, thermal stability, and surface morphology of SG@AA-co-AM. SG@AA-co-AM was utilized as an adsorbent for the removal of Victoria green B (VGB) dye from wastewater. SG@AA-co-AM exhibited a removal percentage (% R) of 97.6% towards VGB under optimized conditions: a contact time of 30 min, temperature of 25 °C, adsorbent dose of 20 mg, pH of 8, concentration of dye solution of 20 ppm, and volume of dye solution of 30 mL. The point of zero charge (PZC) for SG@AA-co-AM was determined to be 5.2. Nonlinear pseudo-second-order (PSO) and Langmuir adsorption isotherm models best fitted to the experimental data, with regression coefficients (R2) of 0.95 and 0.99, respectively. The results confirmed the chemi-sorption and monolayer adsorption of VGB onto SG@AA-co-AM. Thermodynamic studies revealed that the adsorption of VGB onto SG@AA-co-AM is endothermic and spontaneous. Furthermore, the regeneration experiment showed a decline of 3.9% after five cycles, confirming the economical and reusable nature of SG@AA-co-AM.

Cetyltrimethylammonium Bromide-Modified Laponite@Diatomite Composites for Enhanced Adsorption Performance of Organic Pollutants.

This work aims to enhance the adsorption performance of Laponite @diatomite for organic pollutants by modifying it with cetyltrimethylammonium bromide (CTAB). The microstructure and morphology of the CTAB-modified Laponite @diatomite material were characterized using SEM, XRD, FTIR, BET, and TG. Furthermore, the influences of key parameters, containing pH, adsorbent dosage, reaction time, and reaction temperature, on the adsorption process were investigated. The kinetics, thermodynamics, and isotherm models of the adsorption process were analyzed. Finally, potential adsorption mechanisms were given based on the characterization. The research findings indicate that CTAB-La@D exhibits good adsorption performance toward Congo red (CR) over a broad pH range. The maximum adsorption capacity of CR was 451.1 mg/g under the optimum conditions (dosage = 10 mg, contact time = 240 min, initial CR concentration = 100 mg/L, temperature = 25 °C, and pH = 7). The adsorption process conformed to the pseudo-second-order kinetic model, and the adsorption isotherms indicated that the adsorption process of CR was more in line with the Langmuir model, and it was physical adsorption. Thermodynamic analysis illustrates that the adsorption process is exothermic and spontaneous. Additionally, the mechanisms of electrostatic adsorption and hydrophobic effect adsorption of CR were investigated through XPS and FTIR analysis. This work provides an effective pathway for designing high-performance adsorbents for the removal of organic dye, and the synthesized materials hold great capability for practical utilization in the treatment of wastewater.

Silica-coated cellulose using Shorea robusta sawdust biomass and its application for methylene blue dye removal from aqueous solution

Silica-coated cellulose using Shorea robusta sawdust biomass and its application for methylene blue dye removal from aqueous solution

A Facile Synthesis of MgO Decorated Spinel Magnetic Nanoparticles Using Terminalia catappa Leaf Extract: Its Application in EBT Dye Removal

A Facile Synthesis of MgO Decorated Spinel Magnetic Nanoparticles Using Terminalia catappa Leaf Extract: Its Application in EBT Dye Removal

The application of magnetite biochar composite derived from parthenium hysterophorus for the adsorption of methylene blue from aqueous solution

The removal of toxic and harmful dyes like methylene blue (MB) from textile wastewater is necessary to reduce environmental pollution. Therefore, this study is aimed at removing MB from an aqueous solution using magnetite-doped biochar of parthenium hysterophorus. Biochar was prepared through pyrolysis techniques at 500 ℃ for 2 h whereas the magnetite and composite material were developed using coprecipitation methods. Herein, NaNO3 and FeSO4. 7H2O were utilized as precursor materials and NaOH as a precipitating agent for preparation of magnetite. Furthermore, pH point of zero charge (pHpzc), Scanning Electron microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) are characterization techniques used to evaluate the nature of the composite material. On the other hand, a full factorial design involving four factors at two levels (24) such as pH (3 and 9), contact time (10 and 40 min), initial dye concentration (100 and 150 mg/L) and adsorbent dosage of 0.01 and 0.04 g/100 mL was used to design and optimize the batch adsorption of MB from an aqueous solution. As a result, a maximum removal efficiency of 99.99% was attained at optimum operating conditions of pH 9, contact time 40 min, initial MB concentration 100 mg/L and adsorbent dosage of 0.04 g/100 mL. Langmuir, Freundlich and Temkin isotherm models were used to investigate the adsorption isotherm in which Freundlich isotherm with a maximum R2 of 0.98 was found to describe the adsorption process inferring multilayer and heterogeneous surface interaction. Additionally, the thermodynamics study depicts that the nature of the adsorption is spontaneous, endothermic and feasible. On the other hand, the chemosorption nature is revealed by the pseudo second kinetics model with a maximum R2 of 0.99. Finally, the remarkable reusability ranging from 99.98% to 97.6% for five consecutive cycles proved that the magnetic biochar derived from parthenium hysterophorus can be used as an effective adsorbent for the decolourization of MB saturated effluent at an industrial scale.

Utilization of Eco‐friendly Copper Oxide Nanoparticles and Iron Oxide Nanorods in Dye Removal from Real Textile Industry Effluent

AbstractTextile industry wastewater contaminated with dye effluents poses a significant environmental challenge. Numerous nanoparticles are used as adsorbents to treat similarly stimulated wastewater, but particularly nanomaterials synthesized through green methods have gained prominence. To assess their practical applicability in addressing real‐world textile wastewater pollution, studies on dye removal from authentic textile industrial effluents are recommended. As a result, a study focused on the removal of dye from real textile industrial effluent is conducted, and biosynthesized copper oxide nanoparticles and iron oxide nanorods are chosen as adsorbents. The investigation scrutinized the influence of adsorbent dosage, adsorbent‐adsorbate contact time, and wastewater pH on the percentage of dye adsorption. These findings indicate that increasing the adsorbent dosage and contact time leads to a higher percentage of dye removal. Notably, copper oxide nanoparticles exhibit superior dye removal efficiency at pH levels 5 and 7, outperforming the maximum dye removal efficiency of iron oxide nanorods at pH 12. The study achieved an impressive process efficiency of 95.24% for copper oxide nanoparticles and 62.5% for iron oxide nanorods. Response surface methodology (RSM) is employed for statistical data analysis and optimization of dye removal process parameters to maximize efficiency. Overall, the results demonstrate that biosynthesized nanomaterials offer a promising and effective solution for removing dyes from textile industrial wastewater.

Cellulose acetate nanofiber modified with polydopamine polymerized MOFs for efficient removal of noxious organic dyes.

The need to effectively remove toxic organic dyes from aquatic systems has become an increasingly critical issue in the recent years. In pursuit of this objective, polydopamine (PDA)-binary ZIF-8/UiO-66 (MOFs) was synthesized and incorporated into cellulose acetate (CA), producing ZIF-8/UiO-66/PDA@CA composite nanofibers under meticulously optimized conditions. The potential of fabricated nanofibers to remove cationic methylene blue (MB) dye was investigated. Various analysis tools including FTIR, XRD, SEM, zeta potential, BET, tensile strength testing, and XPS were employed. Results revealed a substantial leap in tensile strength, with ZIF-8/UiO-66/PDA@CA registering an impressive 2.8MPa, as a marked improvement over the neat CA nanofibers (1.1MPa). ZIF-8/UiO-66/PDA@CA nanofibers exhibit an outstanding adsorption capacity of 82mg/g, notably outperforming the 22.4mg/g capacity of neat CA nanofibers. In binary dye systems, these nanofibers exhibit a striking maximum adsorption capacity of 108mg/g, establishing their eminence in addressing the complexities of wastewater treatment. Furthermore, the adsorption data fitted to the Langmuir isotherm, and the pseudo-second-order kinetic model. The fabricated nanofiber demonstrates good reproducibility and durability, consistently upholding its performance over five cycles. This suite of remarkable attributes collectively underscores its potential as a robust, durable, and highly promising solution for the effective and efficient removal of pernicious MB dye, in the context of both water quality improvement and environmental preservation.

One‐pot Green Approach for Rapid and Effective Anionic Dye Remediation: Encapsulation within Alginate Nanocapsules

AbstractBACKGROUNDThe encapsulation technique was applied to efficiently eliminate the Congo red (CR) from aqueous solutions. During the ionotropic gelation between Ca2+ ions and alginate (AL), CR was effectively entrapped within the AL nanocapsules in a one‐step process. Suitable conditions for efficient CR removal via encapsulation were revealed by the systematic optimization of parameters including pH, time, rpm, etc.ResultsAccording to the experimental observations, the stirring rate and temperature were found to have an insignificant effect on the encapsulation of CR molecules. When the pH value of the medium was 3, the highest level of encapsulation efficiency was achieved in a period of 15 min. At a preliminary CR concentration of 2000 mg/L and a pH value of 3, the encapsulation efficiency was calculated to be about 98.9%, with an encapsulation capacity of 2800 mg dye/g AL. The zeta potential values of AL and CR/AL nanocapsules were determined to be +7.05 eV and ‐14.9 eV and the results showed that the particles tended to agglomerate. TEM micrographs also showed that the nanopasscules were nanosized and agglomerated. Soil and UV degradation studies showed that the dye‐entrapped nanocapsules were noted to degrade remarkably. These results seriously highlighted the potential of encapsulation for dye removal in terms of the economical and practical applications.ConclusionEncapsulation was confirmed to be an economical and practical technique for effectively eliminating Congo red from aqueous solutions. Under UV light irradiation, the dye molecules entrapped within alginate nanocapsules displayed photodegradation.This article is protected by copyright. All rights reserved.

Visible Light-Induced Photocatalytic Degradation of Methylene Blue Using Copper-Doped Carbon Dots One-Step Derived from CCA-Wood

Developing novel eco-friendly broad-spectrum visible light photocatalysts for dye removal is one of the urgent problems for water treatment. Here, copper-doped carbon dots (CDs) were reported to be directly fabricated from chromated copper arsenate (CCA) wood waste for the photocatalytic degradation of the methylene blue dye. The properties of the resulting CDs were thoroughly characterized and analyzed, preceding an investigation into the adsorption kinetics of dye degradation. The kinetic study showed that reactant concentration was the rate-limiting factor. The obtained CDs showed a 151 mg/g photocatalytic degradation capacity. Comparing pure CDs to CDs/TiO2 composites, the former demonstrated higher photodegradation efficiency. This superiority can be attributed to the synergistic action of adsorption and photocatalytic degradation working in tandem. This study prepared Cu doped CDs and elucidated the photocatalysis mechanism of methylene blue degradation by CDs. The photodegradation of organic dyes through CDs derived from waste CCA wood emerges as an eco-friendly, facile, and highly efficient method.

Development and application of modified biocarrier immobilized with Bacillus sp. for azo dye degradation: batch and continuous study

The rapid growth of the industry and urbanization induces the consumption of large amounts of freshwater. In the meantime, untreated or partial treatment of industrial (especially textile) wastewater creates a threat to the living system. Azo dyes are generally used in textile industries and cause hazardous effects due to their recalcitrant and toxic nature. The present work emphasized the synergetic effect of adsorption and biodegradation of a modified biocarrier on Congo red (CR) dye removal. The modified biocarrier was developed by entrapping the polyurethane foam and activated carbon with sodium alginate. The adsorption effect was better explained by the Langmuir isotherm than Freundlich isotherm. Various independent factors, including pH, dissolved oxygen (DO), and dye concentration, were optimized in a fixed bed bioreactor (FBBR) filled with Bacillus sp. immobilized modified biocarrier. The highest removal of 95.43% was evaluated at a pH of 7.0, DO of 5.0 mg O2/L, and inlet CR dye concentration of 100 mg/L. Moreover, the continuous operation of FBBR achieved a 91.13% dye removal at an inlet loading rate of 216 mg/L. d at an initial dye concentration of 300 mg/L. The present approach could be an efficient technology for azo dye treatment.

Green synthesized Cu-doped CeO2 nanoparticles for Congo red dye adsorption and antibacterial action

The removal of pollutants from water bodies is crucial for the well-being of humanity and is a topic of global research. Researchers have turned their attention to green synthesized nanoparticles for wastewater treatment due to their eco-friendly nature, biocompatibility, and cost-effectiveness. This work demonstrates the efficient removal of organic dye and both gram-positive and gram-negative bacteria from water bodies using copper-doped cerium oxide nanoparticles synthesized with Murraya Koenigii extract. Characterized via various methods, the 15% copper doped cerium oxide nanoparticles (Cu 15% NPs) exhibited maximum Congo red dye adsorption (98% degradation in 35 min). Kinetic analysis favoured a pseudo-second-order model, indicating the chemical nature of adsorption. Equilibrium adsorption isotherms aligned with the Langmuir model, indicating homogenous monolayer dye adsorption on the doped adsorbent. The maximum uptake of adsorbate, Q m obtained from Langmuir model for Cu 15% NPs was 193 mg g−1. The study also showed enhanced antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa for Cu-doped ceria, attributed to generation of reactive oxygen species (ROS) induced by the redox cycling between Ce3+ and Ce4+. This substantiated that the green synthesized copper doped cerium oxide nanoparticles are potential candidates for adsorptive removal of Congo red dye and as antibacterial agents.

The application of synthesized geopolymer for the removal of cationic dye from industrial wastewater

In this study, a low-cost and effective coal fly ash porous geopolymer (CFPG) was prepared through alkali activation and applied as adsorbent for the removal of Rhodamine B (RhB) from real industrial wastewater. Mineral composition, microstructural analysis and surface chemistry were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. The batch experiment was investigated at different CFPG dose (0.4–2 g), RhB concentration (5–30 mg/L), pH (2, 7 and 10) and contact time (30–300 min). The removal efficiency for the adsorption of RhB using CFPG was affected by dosage, concentration, and time. However, removal efficiency of 100 % was achieved at pH (2, 7 and 10) indicating that the adsorbent can be used in wide pH range owing to the zwitterionic nature of RhB. The findings demonstrated that while increasing the initial dye concentration resulted in a decrease in removal efficiency, increasing the CFPG dose and contact time led to an improvement in removal efficiency. Additionally, for specified values of examined parameters, such as CFPG dose of 2 g, initial RhB dye concentration of 5 mg/L, and contact time of 300 min, the maximum efficiency of 100 % was achieved for RhB dye removal. The study on removal efficiency of CFPG on selective dyes showed that it could also be used to remove other cationic dyes such as malachite green and crystal violet in industrial wastewater as removal efficiency of 100 % was obtained for the removal of both dyes. Pseudo-first-order (R2 = 0.985) and Freundlich (R2 = 0.860) models were most suitable for the adsorption process.

The Biosorption Capacity of the Marine Microalga Phaeodactylum tricornutum for the Removal of Toluidine Blue from Seawater

A wide variety of dyes, such as toluidine blue (TB), are used daily for a multitude of purposes. After use, many of these compounds end up in aqueous effluents, reaching natural environments, including marine environments. The removal of these pollutants from marine environments must be considered a priority problem. The search for natural techniques, such as biosorption, is a preferred option to eliminate pollution from natural environments. However, biosorption studies in seawater are scarce. For this reason, the living biomass of the marine microalga Phaeodactylum tricornutum was studied to determine its ability to remove TB from seawater. The kinetics of the biosorption process, the isotherms, and the effect of light and pH were determined. This biomass showed a maximum TB removal capacity of 45 ± 2 mg g−1 in the presence of light. Light had a positive effect on the TB removal capacity of this living biomass. The best fitting kinetics was the pseudo-second order kinetics. The efficiency of the removal process increased with increasing pH. This removal was more effective at alkaline pH values. The results demonstrated the efficacy of P. tricornutum living biomass for the efficient removal of toluidine blue dye from seawater both in the presence and absence of light.

Advances and feasibility of biocatalytic technologies for dye removal

The expanding dye and dye-related industries have led to the production of large volumes of dye-containing wastewater streams. Without adequate treatment, the wastewater could pollute the environment and give rise to health concerns. Biocatalytic technologies provide a channel of treating the wastewater. These technologies involve immobilizing dye-degrading enzymes particularly laccase and peroxidase, and microorganisms on or in suitable supports to enhance their activities, stability, efficiency, and recyclability. This review provides the latest advances in biocatalytic technologies and their feasibility. Based on this review, laccase has been immobilized on supports comprising PEDOT-PPy-COOH/Pt, nanocellulose from quinoa husks, calcium alginate, delignified spent grain, polymeric membrane, and metal-organic frameworks to treat different dyes with efficiencies ranging from 39% to 100%. Peroxidase has been immobilized on calcium alginate, Fe3O4 nanoparticles, cationic maize starch, and graphene oxide-SiO2 for treatment of various dyes with efficiencies in the range of 40–100%. The dye-degrading ability of azoreductase is often harnessed through immobilization of microbial cells which contain multiple enzymes in them and are frequently able to decolorize more than 90% of the dyes tested. An immobilized azoreductase has been successfully produced but showed lower dye-degrading efficiencies of 18.3–58.3%. The performance of biocatalysts can be affected by multiple factors, making optimization of the operating conditions important. The use of green support materials could reduce the cost of biocatalysts and the associated environmental concerns. A versatile biocatalyst or biocatalyst mixture is beneficial to degrade the complex pollutants in dye-containing wastewater.